Archery bow having limbs with multiple reversible curvatures

ABSTRACT

An archery bow having multiple reversal curves in the bow limbs wherein the first and second reversal curves in each limb are within a segment which occupies less then half the length of the limb and which is located substantially equidistant from the end of the handle and the tip of the bow.

United States Patent Stewart Aug. 26, 1975 [54] ARCHERY BOW HAVING LIMBS WITH 1,029,716 6/1912 Roe 124/24 R MULTIPLE REVERSIBLE CURVATURES 3,410,644 1 H1968 McLendon 124/24 R X [76] Inventor: William R. Stewart, Rt, 1, Box 1, FOREIGN PATENTS 0R APPLICATIONS Harrah, Wash. 98933 241,085 1/1911 Germany 124/23 R F [22] Dec 1973 Primary ExaminerRichard C. Pinkham [21] Appl. No.: 424,901 Assistant Examiner-William R. Browne 52 US. Cl. 124/24 R; 124/30 R [57] ABSTRACT [51] Int. Cl. F4lb 5/00 An archery bow having multiple reversal curves in the [58] Field of Search 124/23 R, 24 R, 41, 30 R, bow limbs wherein the first and second reversal curves 124/25 in each limb are within a segment which occupies less then half the length of the limb and which is located [56] References Cited substantially equidistant from the end of the handle UNITED STATES PATENTS and the p of the 28,698 6/1860 Stevens 124/25 1 Claim, 4 Drawing Figures ARCHERY BOW HAVING LIMBS WITH MULTIPLE REVERSIBLE CURVATURES BACKGROUND OF THE INVENTION The present-invention relates to an archery bow and is particularly useful in a bow construction of the socalled recurve type. A recurve bowis characterized by each bow limb, as it extends from the bow handle, curving in a direction towards the archer as he holds the bow in shooting position, while at the extremity of the limb the direction of curvature is reversed (recurved) to define a bow tip which projects away from the archer.

The use of a recurve in a bow construction provides several advantages. Inasmuch as a portion of the bow string in the braced, or undrawn, position lies along the surface of the bow tip, it is apparent that when the string is drawn and released, the tip serves to dampen the vibrations set in motion by the string returning to the braced position. This contributes to a quiet bow and one which is smooth to handle. More importantly, however, the use of a recurved tip provides a compound bending action of the bow as the string is drawn bow limb curvature increasing and recurvature at the tip simultaneously being reduced. The force required to accomplish this develops potential energy in the bow, yet the draw of the string necessary to achieve such potential energy is not as great as would be required to produce an equivalent amount in a bow not having recurve (assuming the limb stiffness to be comparable). Nevertheless, with a relatively short recurve tip, the draw force increases substantially for each inch that the bow string is drawn.

Attempts to optimize the benefits of a recurve tip by lengthening it heretofore have resulted in such substantial twisting forces being experienced at the tip that the string slips off the end of the bow. However, the present invention overcomes this problem and permits longer tips to be employed than previously have been possible. Such tips result in the reduction of force necessary to increase the draw, a reduction of bow torque both at the braced position and at the time of arrow release, quieter closing of the bow, lessening of vibrations and recoil during shooting, and reduction of the tendency of the arrow to buckle as it moves past the bow.

The foregoing advantages are achieved by providing in the bow limb between the handle and the tip in a multicurved segment. Such a section serves to reinforce the limb in a manner analogous to corrugation, and thus, the limb is better able to withstand torsional forces. Consequently, the length of the bow tip can be increased without the bow twisting to cause the string to disengage itself from the bow tip.

The invention will be described in greater detail by reference to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein:

FIG. 1 is a side elevational view of a bow incorporating the invention, the bow being unstrung;

FIG. 2 is an end view of the bow shown in FIG. 1;

FIG. 3 is a side elevational view of the bow shown in FIG. 1, except that the bow is strung and is in the braced position; and

FIG. 4 is a diagrammatic view of a portion of the bow shown in FIG. 3, the bow portion being shown in the braced position and at two positions of draw.

Referring now to the drawings, FIGS. 1-3 illustrate the basicelements of a recurve type bow. These include a conventional handle portion 10 and limbs 12 having tips 14 which are provided with grooves, or nocks, 16 and guide channels 18 to receive a string 20. Intermediate the handle 10 and tips 14 each limb 12 is formed with a multicurved segment 22. As shown in FIGS. 1 and 3, the bow is oriented to deliver an arrow from right to left. As the limb 12 extends from the end of the handle 10 (the end being considered as the location at which the handle thickness reduces to substantially that of the limb), the limb is curved to the right in the direction of the archer. Within segment 22 at a location from the handle substantially halfway between the end of the handle and the tip of the limb, the curvature of the limb is reversed a first time and then is reversed a second time thereby defining segment 22 as an elongated S-shape. Beyond segment 22 the direction of curvature of the limb again reverses to form the tip 14.

The bow in its operative state is illustrated in FIG. 4. In the braced position, segment 22 of the limb 12 is shaped in an elongated S fashion with string 20 resting along the length of tip 14. As the string is drawn, the limb 12 flexes with respect to a pivot in the area of handle 10 to increase the limbs curvature. Simultaneously, the recurved tip 14 and the multicurved segment also flex about points intermediate handle 10 and the tip and move towards a straightened position. As a result of these changes in curvatures of the limb, the string 20 lifts off the tip 14. In the arrangement shown in FIG. 4, lift-off is accomplished with the string drawn 17 /2 inches, the distance being measured from point A at the front of the bow to the center of the string.

The 28 inches draw position is shown in FIG. 4 inasmuch as this is the standard position for calibrating the bow. More specifically, the force required to draw the bow 28 inches is used to identify the type of bow. For example, if 50 pounds of force are necessary, the device is designated as a 50 pound bow. Assuming that the bow is of the 50 pound type, it has been found that with conventional recurved tip constructions the force necessary to lengthen the draw increases substantially above 50 pounds for each additional inch of draw beyond 28 inches. However, with a lengthy recurved tip as is permitted by the incorporation of the multicurved segment 22 in the bow limb, a substantially reduced build-up in draw force has been experienced for each inch of draw. This is attributed to the greater leverage achieved by the lengthier bow tip.

In addition to the enhanced draw characteristics just described (called stack in the art), the lengthier recurved tip improves the bow performance when the string is released. As can be seen from FIG. 4, once the string 20 reengages the bow limb, a substantial length of the string contacts the bow thus dampening the string vibrations and reducing the shock of the string slapping against the bow. Thus, the bow closes more quietly and with less recoil and greater smoothness than is possible with conventional recurve bows.

Of course, the multicurved segment 22 resists the tendency of the bow to twist, and during closing this improves the accuracy with which the arrow departs from the bow.

While the bow construction illustrated has integral handle and limb portions, it should be appreciated that the invention is also applicable to knock-down bows wherein the limbs may be detached from the handle.

Furthermore, although the use of a multicurved segment in a bow limb is particularly advantageous in a recurve type bow, it should be appreciated that such a segment also is suitable for use in other bow types wherein increased resistance to limb and tip twisting is desirable. An example of the latter is the construction known in the art as a compound bow.

What is claimed is:

1. An archery bow having a central handle portion and a pair of limbs projecting respectively in opposite directions from the ends of the handle portion, said limbs terminating in tips which are adapted to receive sal. 

1. An archery bow having a central handle portion and a pair of limbs projecting respectively in opposite directions from the ends of the handle portion, said limbs terminating in tips which are adapted to receive a string extending between the tips on one side of the bow, each of said limbs having a curved portion as it projects from the handle and having first and second reversals of curvature within a segment which occupies less than half the length of the limb and which is located substantially equidistant from the end of the handle and the tip, each of said limbs further including a third reversal of curvature leading to said tip, said third reversal being directed away from said one side of the bow and being positioned adjacent said second reversal. 